THE story behind Britain’s first serial killer is to be revealed this week.

Mary Ann Cotton killed 21 people, including her own mother, children and numerous husbands while living in the North East.

But Stephanie Yearnshire, a retired detective superintendent, will be giving a lecture at the University of Sunderland to find out whether she was a mass murderess or a misunderstood matriarch.

Known as the “Black Widow”, Mary Ann Cotton preceded Jack the Ripper and over an eight-year period poisoned her victims with arsenic – and in most cases benefited from their insurance money.

Ms Yearnshire, who worked across the world and won awards in the USA and Australia for her policing work, hopes to enlighten the public on Cotton, who was hanged in Durham Jail in 1873 for the murder of her step-son Frederick Cotton.

The former detective will also ask whether this was the last of a long line of deaths by her hand or if was she a mother caring for her families against a background of poverty and poor medical facilities.

The lecture will be held on Wednesday at the Sir Tom Cowie Campus at St Peter’s. It will start at 2.30pm and last about an hour.

Cotton, who worked at the old Sunderland Infirmary, killed in Hendon, Pallion and Seaham.